Vacuum tube cathode support



1940- c. M. WHEELER EI'AL VACUUM TUBE CATHODE SUPPORT 2 Sheets-Sheet 1 Filed May 9. 1959 ATTORNEY 31, 1940- c. M. WHEELER ETAL VACUUM TUBE CATHODE SUPPORT Filed May 9, 1939 2 Sheets-Sheet 2 2 mi om n Tau N 2 R o VME W m W A mu A em a Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE VACUUM TUBE CATHODE SUPPORT poration of California Application May 9, 1939, Serial No. 272,564

8Claims.

In power tube structures more especially in tubes designed to carry relatively high power it is generally desirable to utilize filamentary cathodes and to provide a plurality of separate filaments which may be supplied from a multiple phase source. In such an arrangement it is necessary to provide a number of filaments equal to the number of phases of the supply source for energizing these tubes. To properly support such filaments a relatively rigid structure is required, in order to prevent the filaments from relative movement with respect to the other electrodes of the tube and consequent poor operation of the tube.

It is an object of our invention to provide a simple and rigid filamentary cathode assembly suitable for use in vacuum tube structures.

It is a further object of our invention to provide a. filament supporting assembly utilizing supporting rods arranged in the form of a closed pattern whereby a rigid assembly of parts is assured.

The filament assembly may comprise three rods arranged in a tripod form with the base of the tripod having a larger diameter than the other end thereof. Arranged outside the tripod and supported at least in part thereby are provided a plurality of filaments forming the cathode. This 0 tripod assembly is mounted on a platform supported on rods sealed through the glass envelope. The above mentioned and further objects of our invention, and the manner of obtaining them, will be apparent from the more complete description of some embodiments of our invention made in connection with the accompanying drawings, in which Fig. 1 illustrates the filament assembly of the vacuum tube structure in accordance with our invention:

Fig. '2 is a plan view of a portion of the cathode structure looking toward plane 2-2;

Figs. 3, 3A, 4, 5 and 6, are sectional views taken along the lines 3-3, 4-4, 55 and 5-6, of Fig. 1;

Fig. 7 is a modified filament assembly structure in section for use in a vacuum tube in accordance with our invention;

Figs. 8 and 9 are cross-sections taken along the lines 8-8 and 9-9 of Fig. 7.

Since other parts of the vacuum tube structure form no part of our invention only the cathode assembly is illustrated. It is understood that the other necessary parts of the tube structure such as anode, grids, etc., may be made in any known manner.

A more detailed description of the cathode assembly is made referring particularly to Figs. 1 to 6, inclusive. The cathode assembly is supported on a glass stem shown generally at III]. This assembly comprises a reentrant stem portion I II through which are sealed nine metallic rods I2I to I29. These rods are preferably of tungsten when the envelope is of glass, known in the trade under the name of Nonex. About these rods and sealed thereto is provided a glass supporting ring II2 for holding them in rigid assembly. Other types of insulating supports may be provided if desired. Six of these rods I2I, I22, I24, I25, I 21, I28, which serve as filament supply leads are offset inwardly to pass through holes provided in a metallic disc H3. The other three of these rods I23, I26, I29, are firmly attached to metallic disc H3 and serve as a tripod platform support. The six rods passing through the platform disc may be insulated therefrom by insulating bushings placed around these rods at the point they pass through the disc, if desired. These six filament leads extending through the disc pass upwardly through a second supporting plate I I5.

Fastened onto the discs II 3 at equally spaced points are three other supporting rods I3 I, I32 and I33, forming the filament supporting structure or tripod. These rods pass through slots provided in disc II5 as shown in Fig. 4. A fourth rod I34 is fastened centrally of disc H3 and passes through the center of plate H5.

Preferably filament lead rods I2I, I24 and I2'I are fastened on the bottom side of disc II5, rods I22, I25 and I28 are fastened on the top side of disc H5 and center rod I34 is fastened both top and bottom. This fastening may be made in any desired manner but one preferred mode of fastening comprises winding of two or three turns of wires about the rods close to the plate I I5 and spot welding each of these wires to the corresponding rod.

Rods I3I, I32 and I33, converge upwardly as they pass through disc I I 5 until at the point 5-5 they are substantially the same distance from center rod I34 as are the filament supporting rods. At this point the filament supporting rods or leads terminate but rods I3I, I32, I33, I34 continue onward. To each of filament leads I2I, I22, I24, I25, I21 and I28, at their terminating ends are fastened separate filaments I4I, I42, I44, I45, I41 and I48, respectively. The rods I3I, I32 and I33, extend outwardly and are fastened to a metallic disc or plate I5II. Also passing through plate I are six short metallic rods I5I, I52, I54, I55, I51, I58, to which. are fastened the other ends of filaments sleeves and then may be firmly held in place by welding. Rod I34 terminates at the disc I I 6 and does not extend therebeyond at which points rods I3II33 cease to converge. Discs H5 and H6 may be of metal or insulating material.

As used in the claims, the expression closed pattern" applied to the arrangement of supporting rods refers to a tripod or a ring shaped grouping of the rods, which assures resistance to lateral bending of the rod assembly.

For maintaining tension on the filaments, rods I5I to ISO- are fastened to a disc arrangement I60 and are slidable in openings in the disc or plate I50. A spring I6I may be compressed between discs I60 and I50, and a bolt nut assembly I62 may be provided for adjusting the compression of spring I6I during the assembly of the tube. The bolt of the assembly-is fastened to disc I50 and passes freely through a hole in disc I60. The bolt and nut hold the spring I6I initially compressed so that the filaments can be put in position after which the nut is unscrewed slightly to permit free action of the spring with respect to the filaments.

With the filament assembly as described above, a six phase supply may be utilized, each filament being heated from a different phase of the supply system. Since the currents in the separate filaments are preferably balanced, no return path is necessary. it being sumcient to connect together the separate filaments. However, should any unbalance occur, the rod assemblies Hi to I33 may serve as return conductors for the filament supply. These rods are connected to rods I23, I26 and I23 which extend outwardly through the envelope and may be connected to ground if desired.

The modified filament assembly illustrated in Fig. '7 is similar to that shown in the other figures,

but is designed for use with filaments of a hairpin type. The particular illustration is designed for use in a tube of smaller dimensions and generally lower power than that of Figs. 1 and 2. The same number of filaments, lead-in rods and supporting rods are shown in the structure of Fig. 7, as in Fig. 2. However, the supporting rods, only one of which 223, appears in the drawings, extend inwardly and are attached to platform disc 2I3. The point of fastening is determined by the disc size used and preferably is made near the outer end of the disc in order to provide a wide supporting base. The supporting rods and tripod rods are preferably fastened to the plate 2I3 in the same manner as those shown in Fig. 1, as illustrated in Fig. 3A. A small sleeve I2 is fastened into plate I I3 or M3 for example by screw threading. Rods such as I29 are tightly fitted into the sleeve and are held in place by arc-welding. The sleeve I2 serves to form a stronger fastening than would be provided by the relatively thin disc, and improves the structure particularly since tungsten tends to crystallize and become brittle upon welding and therefore becomes weaker. By use of the sleeve a support at a distance from the point of welding is provided.

The tripod rods 26I, 262, 263, attached to platform disc 2I3, converge upwardly through the metal supporting member 2I5 and are fastened to the filament supporting plate 250. To this plate is attached hook assemblies 25I to 258 held in place by fastening means such as the insulating beads 250. Preferably a heat shield 28I is provided to protect the bead assembly from the direct heat of the cathode. A drawn metal cap 230 fitted about plate 260 serves to further protect the assembly. The filaments 2, 242, 2, 2", 2", 24!, arefastened atone end to rods 22l, 222, 224, 225, 221, 226, respectively, at one end pass over hooks 2M 252, 254, 266, 251, 266, and on the return and are fastened to the metallic supporting member 2|! preferably by being inserted in holes 23L 232, 234, '235, 231, 233, as shown in Fig. 9. Thus each filament forms a hairpin bend. The return ends of these filaments are connected together at metallic supporting member 2I5 and may be returned to ground through rods 223, 226' and 229, similarly to the return through rods I23, I26 and I23 of Figs. 1 and 2. This alternative filament assembly likewise shows an arrangement suitable for six phase energization, similar to that disclosed in Figs. 1 to 7. In Fig. 7 tripod rods 26! and 263 are partly cut away for clarity.

It should be understood that in each of the embodiments disclosed the filament supporting structure provides a closed pattern support, so that a very rigid assembly of parts is assured. Furthermore the preferred tripod or three leg supporting arrangement assures a stable support throughout the structure.

While we have illustrated our invention in the form of a filament structure suitable for six phase energization, it should .be distinctly understood that any form of energization may be utilized. Furthermore, any desired multiple phase or other energization arrangement may be utilized instead of a six phase system.

Likewise, the supporting tripod elements may converge according to a curve instead of in straight line form as shown. Further, although in the preferred arrangement the support of the electrode structure is made to depend upon the tripod arrangement, it should be understood that other forms of closed pattern supporting arrangements may be utilized within the scope of ourinvention. What we consider to be our invention is defined in the accompanying claims.

What we claim is:

1. A vacuum tube structure comprising a glass stem, a plurality of supporting rods arranged in closed pattern and sealed at one end in said stem, a disc fixed to the other end of said rods and forming a platform therewith, a plurality of secondary rods attached at one end to said disc in a closed pattern arrangement, a plate attached to the other end of said secondary supporting rods, and an electrode supported between said disc and said plate.

2. A vacuum tube structure comprising a glass stem, a plurality of supporting rods arranged in closed pattern and sealed at one end in said stem, a disc fixed to the other end of said rods and forming a platform therewith, a plurality of secondary rods attached at one end to said disc in a closed pattern arrangement, a plate attached to the other end of said secondary supporting rods, a plurality of filament leads extending through said seal and through said disc, and a plurality of filaments supported between said plate and said filament leads.

3. A vacuum tube structure comprising a glass stem, a plurality of supporting rods arranged in closed pattern and sealed at one end in said stem, a disc fixed to the other end of said rods and forming a platform therewith, a plurality of secondary rods attached at one end to said disc in a closed pattern arrangement, a plate attached to the other end of said secondary supporting rods, a plurality of filament leads extending through said seal and through said disc, and a plurality of filaments supported between said plate and said filament leads, and filament tensioning means mounted on said plate for maintaining said filaments under tension.

4. A vacuum tube structure comprising an envelope, a plurality of filament leads extending into said envelope, a plurality of supporting rods extending into said envelope, a disc fastened to the upper end of said supporting rods, supporting means fastened to said disc and extending beyond the ends of said filament leads, a conductive plate supported on the extended end of said supporting means, and a plurality of filaments each connected at one end to one end of said filament leads and at the other end to said conductive plate.

5. A vacuum tube structure comprising a glass stem, a plurality of filament leads and supporting rods, arranged to form a closed pattern, extending through said stem and sealed thereto, a conductive supporting disc fastened to said rods at one end thereof, said filament leads being brought toward each other to form a smaller closed pattern and extending through said disc and insulated therefrom, a plurality of conductive supporting elements fastened to said disc and arranged about said filament leads to form a closed pattern at one end, the other end of said elements being brought together to form a closed pattern of smaller dimension than said smaller filament lead pattern and extending beyond the ends of said filament leads, a metallic plate member mounted on said extended end of said supporting structure, and a plurality of filaments supported by said filament leads and said plate.

6. A vacuum tube filament cathode arrangement, comprising a glass stem, a plurality of symmetrically arranged filament leads and supporting rods extending through said stem and sealed thereto, a metallic disc fastened to said rods, said filament leads extending through said disc and being insulated therefrom, a conductive supporting structure fastened to said disc and extending beyond the ends of said filament leads, a plate member carrying insulated supporting members mounted on the extended end of said supporting structure, a conductive filament supporting means mounted on said supporting structure, and a plurality of filaments, corresponding in number to the number of filament leads, each of said filaments being fastened at one end to a respective one of said filament leads and passing through a corresponding one of said insulating'supporting members and being conductively fastened at its other end to said filament supporting means.

7. A vacuum tube filament assembly comprising a plurality of filament leads, means for supporting said leads in a closed pattern about a circumference, a plurality of filaments supported at one end by said filament leads at their other ends by a plate member to form the outline of a closed cylinder of said circumference, a plurality of supporting rods forming a supporting structure said structure being in the form of a closed pattern larger than said pattern of said filament leads at one end, said supporting rods being offset inwardly to form at the other end a closed pattern smaller than the pattern of said filament leads, and supporting connection between said supporting rods and said plate.

8. A vacuum tube structure comprising a glass stem, a plurality of filament leads and supporting rods, arranged to form a symmetrical closed pattern, extending through said stem and sealed thereto, a conductive supporting disc fastened to said rods at one end thereof, said filament leads being brought toward each other to form a smaller symmetrical closed pattern and extending through said disc and insulated therefrom, a plurality of conductive supporting elements fastened at one end to said disc and arranged about said filament leads to form a symmetrical closed pattern the other end of said elements being brought together to form a symmetrical closed pattern of smaller dimension than said smaller filament lead pattern, and extending beyond the ends of said filament leads, a metallic plate member mounted on said extended end of said supporting structure, and a plurality of filaments supported by said filament leads and said plate.

CARSON M. WHEELER. GEORGE E. DEQUEVAUVILLER. 

